210 METALLURGY OF IRON AND STEEL. This practice is not feasible in most open-hearth plants, but the demands of engineers for pure acid open-hearth steel made it necessary to equip a plant to supply this special product. In order to show that the composition of the metal and slag in the transfer process is the same as in the usual acid furnace, I had samples taken from the bath during different stages of the operation. The metal was tapped from the basic furnace when it contained from 2.50 per cent, to 3.50 per cent, of carbon, and transferred in a molten state to the acid furnace. When the carbon was about 1.00 per cent, the taking of samples was begun. It is seldom that a charge in an acid furnace is higher than this when it is melted, so that the records may be compared with the ordinary acid heat after complete fusion. The results on nine heats are given in Table XII-A, and they may be compared with Table X-B. This latter table shows, under Group I, the composition of slag and metal as found some years ago in an acid furnace running on the usual pig, scrap and ore process. A comparison of the results is shown in Table XII-B. TABLE XII-B. Comparison of Data in Tables X-B and XII-A. Group I. Table X-B Transferred Steel. .54 Min. Max. Ay. 70 to 1 09 88 After Melting ....... ... !8iOa In slag ................ 50.24 42.21 to 53,52 47.95 FeO-4-MnO ........ . ......... 810,-f-I'eO+MnO ........... 45.68 95 82 42.73 to 52.32 47.13 93.42 to 97 65 95 08 13 .17 to .31 23 49,40 49.40 to 50.28 53 62 End of Operation ..... . PeO+MnO ................. 46.29 36.27 to 45 02 41 30 SiO,+FeO-j-MnO ........... 95.69 93.41 to % 68 94 92 The last sample was not always taken just before tapping. Thus in heat D, Table XII-A, the final carbon was not .31 per cent., but the last sample was taken at that point and for the purposes of the investigation this was deemed sufficient. The composition of the slag, both at the earlier and later periods, corresponds to that in former experiments, and if samples had been taken with lower carbons to correspond with the .13 per cent, in Group I, Table X-B, there would have been even a still closer resemblance, as the percentages of metallic oxides would probably have increased.